Tested on a mannequin during NASA’s uncrewed Artemis I lunar flight, the AstroRad radiation vest developed by StemRad and Lockheed Martin can cut solar storm radiation exposure by up to 60%. The targeted garment aims to protect astronauts on future moon and Mars missions.
Radiation remains one of the biggest threats facing deep-space exploration. While astronauts orbiting Earth on the International Space Station enjoy the natural defense of our planet’s magnetic field and atmosphere, those venturing into deep space face radiation levels up to 500 times higher than earthly baselines. During a severe solar particle event, space travelers can potentially absorb a lifetime’s worth of radiation in a matter of days. Occasional solar flares are powerful enough to induce acute illness and significantly raise an astronaut’s long-term cancer risk.
Until recently, space programs relied heavily on retreating into a spacecraft’s shielded safe room and waiting out the solar storm—a process that can span anywhere from a few hours to three days. An alternative option involved cumbersome whole-body suits that offered limited protection. To solve this bottleneck, researchers evaluated a specialized alternative tested during NASA’s uncrewed Artemis I moon mission in late 2022.
The Engineering Behind the AstroRad Vest
Shielding an entire spacecraft against penetrating space radiation proves impractical due to weight restrictions at launch. Recognizing that weight is the bottleneck for deep-space missions, the Israeli-American startup StemRad designed a garment that protects the human body directly rather than blanketing the entire vehicle.
The AstroRad vest weighs about 57 pounds (26 kilograms) on Earth and relies on a high-density plastic rich in hydrogen. Lead is excellent at blocking X-rays and gamma rays on Earth, but when high-energy electrons strike lead, they can trigger a shower of X-rays that are more harmful than the beta particles themselves, while neutron strikes can knock loose a spray of neutrons from the atoms’ nuclei. Hydrogen possesses a high density of electrons without generating those hazardous secondary sprays.
Designers assembled thousands of hexagonal rods of rigid plastic together like scales to create a flexible garment. Rather than attempting a full-body suit, engineers focused protection on the body parts most vulnerable to radiation damage.
“different organs and tissues have very different sensitivities to radiation, so shielding every part of the body equally is not the most effective approach,” study co-author Jordan Houri, lead scientist for space exploration at StemRad, told Space.com. “At the same time, a full-body suit would be much harder to put on and move around in.”
Jordan Houri, lead scientist for space exploration at StemRad
The targeted shielding covers vital organs including the lungs, stomach, bone marrow, digestive system, breasts, and ovaries.
Deep-Space Testing With Phantoms Zohar and Helga
The Artemis I mission carried two life-size adult female test manikins—known as phantoms—seated in NASA’s Orion capsule as it journeyed to the moon and back. Constructed from materials that mimic human tissue, bone, and organs, the manikins were equipped with more than 5,600 radiation sensors on and inside them.
Zohar wore the AstroRad vest during the flight, while Helga flew without a vest. Because the Artemis I flight encountered no major solar storms during its nearly month-long journey, scientists extrapolated the sensor data gathered as the Orion capsule passed through the inner Van Allen radiation belt, simulating extreme solar particle events mirroring historical outbursts from 1972 and 1989.
The simulation results showed that the AstroRad vest could reduce an astronaut’s radiation dose by about 60% during a fierce solar storm comparable to the 1972 event, and by nearly 40% in a calamity mirroring 1989.
Ergonomics, Comfort, and Long-Term Space Missions
Beyond deep-space testing, an early prototype of the vest spent a couple of years on the International Space Station, where five different crew members wore it to evaluate its practicality. That feedback allowed StemRad to refine the ergonomics so the garment can be worn for days on end and even slept in—a crucial capability given that solar particle events can last up to a week.
Researchers chose female body forms for the Artemis I experiment because women are predicted to face a higher risk of radiation-induced cancer due to sensitive tissue distribution.
“Radiation in space is unavoidable, and a single major solar particle event can make a substantial contribution to an astronaut’s lifetime risk of radiation-induced cancer,” study co-author Oren Milstein, CEO and co-founder of StemRad, told Space.com. “By significantly reducing that contribution, personal shielding could be particularly important for future lunar and Mars missions.”
Oren Milstein, CEO and co-founder of StemRad
StemRad developed the vest in partnership with U.S. aerospace giant Lockheed Martin, with funding support from NASA, the German Aerospace Center, and the Israel Space Agency.
Next Steps for Lunar and Martian Exploration
While the short 10-day Artemis II flyby mission did not include the vest due to limited room, engineers anticipate that future crewed Artemis landings on the lunar surface may incorporate personal radiation garments. As NASA pivots toward establishing sustained lunar bases involving stays lasting weeks or months, the likelihood of enduring a dangerous solar storm increases. Mars expeditions, which will require months or years of transit time, face even greater cumulative radiation burdens.
